Communication Between Brains

Have you ever wondered how your newsfeed affects your political views? Why you and your friends have similar opinions on certain matters? Where do your thoughts and ideas originate?

We tend to associate our thinking with our individuality. In reality though, we cannot be defined without the context of the community we are in. In fact, there are significant similarities between individuals since we are constantly influenced by people around us. This outside influence occurs through communication between people. What neural mechanisms underlie such communication? And what do these mechanisms imply for our commonality and individuality?

Professor Uri Hasson at Princeton Neuroscience Institute and Department of Psychology is dedicated to answering these questions. He has investigated brain to brain communication for over ten years. Professor Hasson began his career with studying the function of individual brains. In his 2004 study on the visual response to movies, Professor Hasson noticed a surprising similarity among individuals’ brain activity when subjects were shown the same movie clip. At rest, each subject’s brain exhibited diverse activity– different signal patterns and intensities at the at same brain area. By contrast, during the movie clip, the electrical signals of the subjects’ brains peaked at similar times, exhibiting coordinated neuron firing in a synchronized pattern. In other words, the video, as a means of information communication, triggered a synchronization among human brains. Intrigued, Professor Hasson shifted his focus to the similarities and differences between brains, especially in relation to communication.

To what extent are our brain activities similar when we are exposed to the same information source? When listening to one same real-life story, subjects’ brains showed synchronization in the auditory cortex, language areas, and high-order thinking areas. In comparison, when the same speech was displayed in reverse order, which meant the sound stimulus was the same while the content of the recording was incomprehensible, the similarity pertained only to the auditory area. When the audio was made of scrambled words, synchronization was observed in both language and auditory areas, but not the high order thinking areas. When the sentences were out of order but each sentence was comprehensive, there was synchronization in all three areas– auditory, language, and high order thinking– but the similarity between the high-order areas was less than that resulting from real-life stories. Only when each individual fully understood the material could the maximum synchronization be achieved. These findings suggest that the interpretation of the information is crucial to the coupling of the brain.

Similar patterns between brains also existed in frontal cortex and high-order thinking area when stories were told in different languages, which further demonstrates that it is the interpretation and understanding of the meanings– not of the physical sound stimulus, like scrambled words or an incomprehensible recording– that leads to the coupling between brains. For example, when telling the same story to people in two different countries, each person’s brain signals are synchronized even though the story is told in different languages.

We can communicate because we have this common code that presents meaning.

The coupling of brain activities underlies the information transfer between brains. Since the synchronization can represent the level of understanding of the material, the more similar the brain activities of the speaker and listener are, the better the listener understands the speaker. In a 2010 study, human subjects listened to spoken stories while their neural dynamics were being recorded. After assessing individuals’ comprehension of the story with questionnaires, Professor Hasson discovered that “listeners’ brain activity mirrors the speaker’s brain activity” and that the “extent of speaker-listener neural coupling predicts the success of the communication.” In addition, in one experiment, when the listener was able to predict the speaker’s word choice in the description of a picture, the brain activities of the listener and speaker became more synchronized, improving the efficacy of the communication.

The synchronization between brain signals does not mean that we have no individuality. In a recent 2015 study, when the subjects with different prior knowledge were exposed to the same piece of information, variations in the brain activities were observed. In one experiment, when subjects were given different background information before listening to a story, their interpretations varied, leading to variations in brain activities. In this sense, our prior experience and memory can influence our opinions when looking at the same piece of information. In reality, the media, life experience, and personal belief can all be sources of such variation, which represents our individuality. However, when looking at this matter in the scope of society as a whole, we should be concerned if the gap between different social groups is so big that no common ground is left for understanding each other. Thus, Professor Hasson suggests, “Maybe one way to do it is to go back to the more natural way of communication, which is a dialogue, in which I am speaking and I am listening, and together we are trying to come to a common ground and new ideas. Because after all, the people we are coupled to define who we are.”